1. Technical Field
The invention relates to spool support structures used within gas turbine engines in general, and to spool support structures for multi-spool gas turbine engines in particular.
2. Background Information
A gas turbine engine can include a fan, a low pressure compressor, a high pressure compressor, a combustor section, a low pressure turbine, and a high pressure turbine disposed along a common longitudinal axis. The fan and compressor sections work the air drawn into the engine, increasing the pressure and temperature of the air. Fuel is added to the worked air and the mixture is burned within the combustor section. The combustion products and any unburned air subsequently power the turbine sections and exit the engine producing thrust. A low pressure spool (sometimes referred to as an “axial shaft”) connects the low pressure compressor and the low pressure turbine. A high pressure spool (sometimes referred to as an “axial shaft”) connects the high pressure compressor and the high pressure turbine. The low pressure spool and high pressure spool are rotatable about the longitudinal axis.
It is known to use support frames (e.g., circumferentially distributed struts) to support the low and high pressure spools. The support frames extend radially toward the respective spool and have a bearing disposed at a distal end, which bearing is in contact with the spool. The bearings facilitate rotation of the spools and provide a load path between the spool and the support frame.
The angular momentum (“L”) of the axial shaft, which is a function of its angular velocity (“ω”), imparts a torque to the frame to which the bearing is mounted. The torque, in turn, creates shear stress within the frame. To accommodate the torque and concomitant stress, the frame includes a structure often referred to as a “torque box”. The torque box accommodates the stress, but adds to the weight and cost of the engine.
What is needed, therefore, is an apparatus for supporting the spools that can accommodate the loadings attributable to the angular momentum of the spools.